Induction of neuronal and inducible nitric oxide synthase in the motoneurons of spinal cord following transient abdominal aorta occlusion in rats

Effects of Ganoderma lucidum Polysaccharides on Different Pathways Involved in the Development of Spinal Cord Ischemia Reperfusion Injury: Biochemical, Histopathologic, and Ultrastructural Analysis in a Rat Model

OBJECTIVE

Inflammation and oxidative stress are 2 important factors in the emergence of paraplegia associated with spinal cord ischemia-reperfusion injury (SCIRI) after thoracoabdominal aortic surgery. Here it is aimed to investigate the effects of Ganoderma lucidum polysaccharide (GLPS) on SCIRI.

METHODS

Rats were randomly selected into 4 groups of 8 animals each: sham, ischemia, methylprednisolone, and GLPS. To research the impacts of various pathways that are efficacious in formation of SCIRI, tumor necrosis factor α, interleukin 1β, nitric oxide, superoxide dismutase levels, and catalase, glutathione peroxidase activities, malondialdehyde levels, and caspase-3 activity were measured in tissues taken from the spinal cord of rats in all groups killed 24 hours after ischemia reperfusion injury. The Basso, Beattie, and Bresnahan locomotor scale and inclined plane test were used for neurologic assessment before and after SCIRI. In addition, histologic and ultrastructural analyses of tissue samples in all groups were performed.

RESULTS

SCIRI also caused marked increase in tissue tumor necrosis factor α, interleukin 1β, nitric oxide, malondialdehyde levels, and caspase-3 activity, because of inflammation, increased free radical generation, lipid peroxidation, and apoptosis, respectively. On the other hand, SCIRI caused significant reduction in tissue superoxide dismutase, glutathione peroxidase, and catalase activities. Pretreatment with GLPS likewise diminished the level of the spinal cord edema, inflammation, and tissue injury shown by pathologic and ultrastructural examination. Pretreatment with GLPS reversed all these biochemical changes and improved the altered neurologic status.

CONCLUSIONS

These outcomes propose that pretreatment with GLPS prevents progression of SCIRI by alleviating inflammation, oxidation, and apoptosis.

Allicin protects spinal cord neurons from glutamate-induced oxidative stress through regulating the heat shock protein 70/inducible nitric oxide synthase pathway

Allicin, the main biologically active compound derived from garlic, exerts a broad spectrum of pharmacological activities and is considered to have therapeutic potential in many neurological disorders. Using an in vitro spinal cord injury model induced by glutamate treatment, we sought to investigate the neuroprotective effects of allicin in primary cultured spinal cord neurons. We found that allicin treatment significantly attenuated glutamate-induced lactate dehydrogenase (LDH) release, loss of cell viability and apoptotic neuronal death. This protection was associated with reduced oxidative stress, as evidenced by decreased reactive oxygen species (ROS) generation, reduced lipid peroxidation and preservation of antioxidant enzyme activities. The results of western blot analysis showed that allicin decreased the expression of inducible nitric oxide synthase (iNOS), but had no effects on the expression of neuronal NOS (nNOS) following glutamate exposure. Moreover, allicin treatment significantly increased the expression of heat shock protein 70 (HSP70) at both mRNA and protein levels. Knockdown of HSP70 by specific targeted small interfere RNA (siRNA) not only mitigated allicin-induced protective activity, but also partially nullified its effects on the regulation of iNOS. Collectively, these data demonstrate that allicin treatment may be an effective therapeutic strategy for spinal cord injury, and that the potential underlying mechanism involves HSP70/iNOS pathway-mediated inhibition of oxidative stress.

The impact of discrete modes of spinal cord injury on bladder muscle contractility

Background

Prior studies have compared the effect of spinal cord injury elicited using distinct approaches on motor and visceral function. However, the impact of such discrete modes of injury specifically on bladder muscle contractility has not been explored in detail. The goal of this study is to compare the impact of complete spinal cord transection versus clip compression at thoracic vertebra eight (T8) on bladder muscle contractility.

Methods

Rats underwent no treatment (Control), laminectomy (Sham, SH); complete extradural transection (TX); or cord compression with an aneurysm clip (CX). Bladders and spinal cords were harvested at 6 wk for contractility studies or histological analysis.

Results

Detrusor strips from TX and CX rats showed higher spontaneous activity than those from SH rats. Furthermore, the duration of the neurally-mediated contractile response was longer in TX and CX rats compared to controls and showed attenuated relaxation. No significant differences were observed between muscle strips from SH, TX or CX rats in response to KCl, ATP or phenylephrine. However, tissues from TX and CX rats showed a higher sensitivity to carbachol compared to that from SH animals.

Conclusions

Complete SCI in rats either by cord transection or compression elicits qualitatively similar changes in bladder muscle contractility. Whereas cord transection is arguably easier to perform experimentally, cord compression better models the situation observed clinically, such that each approach has clear advantages and limitations.

Acute effect of Ghrelin on ischemia/reperfusion injury in the rat spinal cord

Ghrelin, a 28-amino acid peptide, is mainly secreted by the stomach. Ghrelin has been shown to have neuroprotective effects. However, whether ghrelin protects the spinal cord from ischemia/reperfusion (I/R) injury is unknown. To investigate this, 60 rats were randomly divided into three different groups: the sham group (n = 20), the vehicle group (n = 20), and the Ghrelin group (100 μg/kg, n = 20). Rats were sacrificed 12, 24, 48 and 72 h after ischemia. After the evaluation of neurologic function (48 h), the spinal cords were immediately removed for the determination of myeloperoxidase (MPO) activity (12-72 h). Apoptosis was quantitatively measured using the terminal transferase UTP nick end-labeling (TUNEL) method (24 h). The expression of bax and bcl-2 were evaluated by Western blot analysis (1 h), and GHSR-1a mRNA expression was detected using reverse transcriptase polymerase chain reaction (24 h). The neurological motor function was evaluated by 'Tarlov's score'. The neurologic outcomes in the ghrelin-group were significantly better than those in the vehicle group (p < 0.05). Serum tumor necrosis factor (TNF-α) levels were assessed in the peripheral venous blood. Ghrelin decreased the serum TNF-α levels and ameliorated the down regulation of spinal cord MPO activity. The expression of ghrelin receptors (GHSR-1a) in the rat spinal cord was decreased by I/R injury and increased by ghrelin. Ghrelin reduced the TUNEL-positive rate. Greater bcl-2, HSP27, HSP70, and attenuated bax expression were observed in the ghrelin-treated rats. Our results suggest that ghrelin administration may inhibit spinal I/R injury. Moreover, the improvement of neurologic function in rats was increased after the ghrelin treatment.

Rosuvastatin, a new generation 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitor, reduces ischemia/reperfusion-induced spinal cord tissue injury in rats

BACKGROUND

Severe neurological injury still represents one of the most devastating complications occurring after surgical repair of thoracoabdominal aneurysms. We aimed to investigate the role of rosuvastatin (RSV) against ischemia/reperfusion injury in an experimental model of spinal cord ischemia in rats.

METHODS

Experimental groups included control group (n = 8), ischemia/reperfusion group (n = 8) undergoing aortic occlusion without pharmacologic treatment, and RSV-treated group (n = 8) receiving 10 mg/kg/day of RSV orally for 3 days before spinal cord ischemia. Spinal cord ischemia was induced by occlusion of the abdominal aorta between the left renal artery and aortic bifurcation for 45 minutes, followed by reperfusion. Neurological status was assessed before spinal ischemia and at 48 hours postoperatively. Spinal cords were harvested for histopathologic examination with hematoxylin-eosin staining and biochemical analysis for tissue malondialdehyde, superoxide dismutase, and glutathione peroxidase levels.

RESULTS

Decreased spinal cord tissue malondialdehyde levels (p = .01) and increased tissue superoxide dismutase (p = .01) and glutathione peroxidase (p = .09) levels were observed in the RSV-treated group, as compared with the ischemia group. Histopathologic analyses demonstrated typical changes of ischemic necrosis in the ischemia group; however, RSV attenuated tissue necrosis. Total injury score in the RSV-treated group was significantly decreased, as compared with the ischemia group (p < .05). The Tarlov scores at 48 hours postoperatively were higher in the RSV group as compared with the ischemia group.

CONCLUSION

RSV administration before spinal cord ischemia reduces spinal cord tissue injury by increasing antioxidant enzyme levels and may reduce the incidence of associated neurological dysfunction.

Preconditioning of isoflurane on spinal cord ischemia can increase the number of inducible nitric oxide synthase-expressing motor neurons in rat

Background

Spinal cord ischemia with resulting paraplegia remains one of the most common complications after repair of thoracoabdominal aortic aneurysms or dissection. Inducible nitric oxide synthase (iNOS) is known to have both neuroprotective and neurotoxic effects in the central nervous system. We investigated the possible relationship between the effect of pre-ischemic isoflurane exposure on mild spinal cord ischemia and the inducible nitric oxide synthase (iNOS) expression by using iNOS-specific antibody and pyrrolidinedithio carbamate (PDTC), NF-κB inhibitor, in the ventral horn of spinal cord in rats.

Methods

The animals were divided into five groups (n = 6 in each group): sham group, control group, PDTC-treated group, isoflurane-treated group, and PDTC/ isoflurane-treated group. In the PDTC-treated groups, 2% 100 mg/kg PDTC was administered intraperitoneally at 1 h before operation and at 24 h and 48 h after reperfusion. The rats in the isoflurane-treated groups received 30 min inhalation of 2.8% isoflurane at 24 h before spinal cord ischemia. Immunohistochemistry was performed to detect iNOS expression in the motor neuron of the ventral horn in spinal cord.

Results

Preconditioning with isoflurane increased the iNOS expression when compared to the control group (P < 0.05), whereas pre-treatment with both PDTC and isoflurane significantly decreased the iNOS expression compared to isoflurane-treated group (P < 0.05).

Conclusions

Pre-ischemic isoflurane exposure was related with increase of the iNOS expression via a pathway modulated by NF-κB. iNOS may act as an important mediator of delayed preconditioning with isoflurane for the protective effect against spinal cord ischemia.

Region-specific sensitivity of the spinal cord to ischemia/reperfusion: the dynamic of changes in catalytic NOS activity

This study was designed in order to consider whether the release of neuronally derived nitric oxide (NO) in the lumbosacral spinal cord during ischemia/reperfusion is region-specific and whether changes in Ca(2+)-dependent NO synthase (cNOS) activity paralell with functional outcome. The cNOS activity was measured in the spinal cord regions after 13-, 15- and 17-min ischemia alone and that followed by 24 h of reperfusion. In addition, the Tarlov's criteria were applied to define the neurological consequences of ischemia/reperfusion in experimental animals. Based on the results, it is evident that only the 17-min ischemia alone was quite sufficient to cause changes in cNOS activity, however, without alterations in functional outcomes. On the other hand, the ischemic episodes followed by reperfusion caused dynamic, region-specific alterations in cNOS activity and consequently led to deterioration of motor function of hindlimbs in affected animals. Our results indicate that the motoneurons in the ventral horns respond more sensitively to ischemia/reperfusion than do neurons localized in the other spinal cord regions and that changes in cNOS activity may also influence the axonal conductance in the white matter and account for the impairment of motoneuronal activity in affected animals.

Nitrotyrosine in human neonatal spinal cord after perinatal asphyxia

BACKGROUND

Spinal cord injury has been reported after perinatal asphyxia in full-term neonates.

OBJECTIVES

To examine the role of excessive nitric oxide production in perinatal spinal cord injury.

SUBJECTS AND METHODS

Tissue samples of 18 full-term neonates who died of hypoxic-ischemic encephalopathy were analyzed for the presence of nitrotyrosine (NT).

RESULTS

NT was demonstrated in 5 of these 18 neonates. In addition, activated caspase 3, a marker of apoptosis, and CD68, as a marker of inflammation, could be demonstrated in some infants.

CONCLUSIONS

excessive nitric oxide production and subsequent NT formation is seen in spinal cord tissue after severe perinatal asphyxia. This finding may be relevant for the development of neuroprotective strategies.

Real-time direct measurement of spinal cord blood flow at the site of compression: relationship between blood flow recovery and motor deficiency in spinal cord injury

STUDY DESIGN

An in vivo study to measure rat spinal cord blood flow in real-time at the site of compression using a newly developed device.

OBJECTIVES

To evaluate the change in thoracic spinal cord blood flow by compression force and to clarify the association between blood flow recovery and motor deficiency after a spinal cord compression injury.

SUMMARY OF BACKGROUND DATA

Until now, no real-time measurement of spinal cord blood flow at the site of compression has been conducted. In addition, it has not been clearly determined whether blood flow recovery is related to motor function after a spinal cord injury.

METHODS

Our blood flow measurement system was a combination of a noncontact type laser Doppler system and a spinal cord compression device. The rat thoracic spinal cord was exposed at the 11th vertebra and spinal cord blood flow at the site of compression was continuously measured before, during, and after the compression. The functioning of the animal's hind-limbs was evaluated by the Basso, Beattie and Bresnahan scoring scale and the frequency of voluntary standing. Histologic changes such as permeability of blood-spinal cord barrier, microglia proliferation, and apoptotic cell death were examined in compressed spinal cord tissue.

RESULTS

The spinal blood flow decreased on each increase in the compression force. After applying a 5-g weight, the blood flow decreased to <40% of the precompression level. Complete ischemia was reached using a 20-g weight. After decompression, the blood flow level in the 20-minute complete ischemia group was significantly higher than that in the 40-minute complete ischemia group. The hind-limb motor function in the 40-minute complete ischemia group was significantly less than that in the sham group (without compression), while no significant difference was observed between the 20-minute ischemia group and the sham group. In the 20-minute ischemia group, the rats whose spinal cord blood flow recovery was incomplete showed significant motor function loss compared with rats that completely recovered blood flow. Extensive breakdown of blood-spinal cord barrier integrity and the following microglia proliferation and apoptotic cell death were detected in the 40-minute complete ischemia group.

CONCLUSION

Duration of ischemia/compression and blood flow recovery of the spinal cord are important factors in the recovery of motor function after a spinal cord injury.

The correlation between nitric oxide and vascular endothelial growth factor in spinal cord injury

STUDY DESIGN

Prospective, randomized, placebo-controlled, experimental study.

OBJECTIVES

The issue of whether nitric oxide (NO) production is beneficial or deleterious on ischemic injuries of the central nervous system still remains doubtful. Vascular endothelial growth factor (VEGF) is known to induce the release of NO from endothelial cells. However, the effect of NO on VEGF synthesis is not clear. We aimed to determine the effects of L-arginine and NG-nitro-L-arginine methyl ester (L-NAME) on VEGF synthesis and free radicals in a rat model of spinal cord ischemia-reperfusion (IR) injury.

SETTING

Surgical Research Laboratory of a Medical School.

MATERIAL AND METHODS

Twenty-eight Wistar rats were divided into four groups as follows (n=7): Sham, IR injury, L-arginine, and L-NAME. Infrarenal abdominal aorta was occluded to induce spinal cord ischemia. L-Arginine (100 mg/kg) and L-NAME (10 mg/kg) were given before aortic occlusion. Biochemical assays of malondialdehyde (MDA), NO and VEGF were carried out in spinal cord specimens.

RESULTS

L-Arginine treatment significantly increased MDA and NO, but decreased VEGF levels in spinal cord. However, nonselective inhibition of NOS with L-NAME significantly decreased MDA and NO, but increased VEGF levels. Besides, the positive linear correlation between MDA and NO, and negative linear correlations between MDA, NO and VEGF levels have also been demonstrated.

CONCLUSION

Nonselective inhibition of NO synthase activity with L-NAME attenuated free radical formation and increased VEGF level when compared with NO precursor L-arginine in a rat model of spinal cord ischemia. We suggest that inhibition of NO synthase, as well as induction of VEGF, may be a therapeutic option in spinal cord IR injury.

Protective effect of intrathecal ketorolac in spinal cord ischemia in rats: a microdialysis study

BACKGROUND

The prevention of ischemic paraplegia after thoracoabdominal aortic surgery is challenging for both anesthesiologists and surgeons. In a previous study, we showed that intrathecal ketorolac pre-treatment protects rats against ischemic spinal cord injury. In the present study, using a microdialysis method, we investigated whether this neuroprotective effect was related to changes in the spinal cord release of nitric oxide (NO) or the excitatory amino acids (EAAs) aspartate and glutamate.

METHODS

Rats were randomized to receive either intrathecal saline or ketorolac 60 microg (10 rats per group), 1 h before spinal cord ischemic injury induced by balloon inflation of a 2F Fogarty catheter in the thoracic aorta with maintenance of the proximal arterial blood pressure at 40 mmHg for 11 min, followed by reperfusion. Another 10 animals were used as the sham-operated control group. Ischemic injury was assessed by hind limb motor function. Cerebrospinal fluid dialysates were collected at baseline (before ischemia) and at 1, 2, 3, 4, 6, 12 and 24 h after the start of reperfusion, and were analyzed for EAAs using high-performance liquid chromatography and for NO metabolites using an NO analyzer.

RESULTS

The results showed that intrathecal ketorolac attenuated spinal cord ischemic injury. Dialysate concentrations of NO and EAAs were increased after spinal cord ischemia, and this effect was inhibited by intrathecal administration of ketorolac.

CONCLUSIONS

The results of this study suggest that the neuroprotective effect of intrathecal ketorolac in spinal cord ischemia in rats may be caused by a decrease in the spinal cord release of NO and EAAs.

Neuronal Nitric Oxide Synthase Immunopositivity in Motoneurons of the Rabbit's Spinal Cord After Transient Ischemia/Reperfusion Injury

1. Motoneurons in the spinal cord are especially vulnerable to ischemic injury and selectively destroyed after transient ischemia. To evaluate the role of nitric oxide (NO) in the pathophysiology of the spinal cord ischemia, the expression of neuronal nitric oxide synthase (nNOS) in the motoneurons of the lumbosacral spinal cord was examined in the rabbit model of transient abdominal aorta occlusion. 2. The aim of the present study was to find if there is any consensus between the duration of transient abdominal aorta occlusion, nNOS positivity of the motoneurons and neurological hind limb impairment. 3. According to the degree of neurological damage (i.e., from the group with almost no sign of damage to a group with fully developed paraplegia), the experimental animals were divided into three groups. The respective spinal cord segments of each experimental group were compared to the control group. 4. Spinal cord ischemia (15 min) was induced by Fogarty arterial embolectomy catheter occlusion of abdominal aorta with a reperfusion period of 7 days. On seventh day, the sections of lumbosacral segments were immunohistochemically treated and L1-L7, and S1-S2 segment sections were monitored using light microscopy.

Spatiotemporal Alterations of the NO/NOS Neuronal Pools Following Transient Abdominal Aorta Occlusion: Morphological and Biochemical Studies in the Rabbit

1. Brief interruption of spinal cord blood flow resulting from transient abdominal aortic occlusion may lead to degeneration of specific spinal cord neurons and to irreversible loss of neurological function. The alteration of nitric oxide/nitric oxide synthase (NO/NOS) pool occurring after ischemic insult may play a protective or destructive role in neuronal survival of affected spinal cord segments. 2. In the present study, the spatiotemporal changes of NOS following transient ischemia were evaluated by investigating neuronal NOS immunoreactivity (nNOS-IR), reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry, and calcium-dependent NOS (cNOS) conversion of [(3)H] l-arginine to [(3)H] l-citrulline. 3. The greatest levels of these enzymes and activities were detected in the dorsal horn, which appeared to be most resistant to ischemia. In that area, the first significant increase in NADPHd staining and cNOS catalytic activity was found immediately after a 15-min ischemic insult. 4. Increases in the ventral horn were observed later (i.e., after a 24-h reperfusion period). While the most intense increase in nNOS-IR was detected in surviving motoneurons of animals with a shorter ischemic insult (13 min), the greatest increase of cNOS catalytic activity and NADPHd staining of the endothelial cells was found after stronger insult (15 min). 5. Given that the highest levels of nNOS, NADPHd, and cNOS were found in the ischemia-resistant dorsal horn, and nNOS-IR in surviving motoneurons, it is possible that NO production may play a neuroprotective role in ischemic/reperfusion injury.

Effect of ischemia in vivo and oxygen-glucose deprivation in vitro on NOS pools in the spinal cord: comparative study

1. This study was performed to compare both the Ca(2+)-dependent nitric oxide synthase (NOS) activity and the neuronal nitric oxide synthase immunoreactivity (nNOS-IR) in the rabbit lumbosacral spinal cord after 15 min abdominal aorta occlusion (ischemia in vivo) and oxygen-glucose deprivation of the spinal cord slices for 45 and 60 min (ischemia in vitro). All ischemic periods were followed by 15, 30 and 60 min reoxygenation in vitro. 2. Catalytic nitric oxide synthase activity was determined by the conversion of (L)-[(14)C]arginine to (L)-[(14)C]citrulline. Neuronal nitric oxide synthase immunoreactivity in the spinal cord was detected by incubation of sections with polyclonal sheep-nNOS-primary antibody and biotinylated anti-sheep secondary antibody. 3. Our results show that ischemia in vivo and the oxygen-glucose deprivation of spinal cord slices in vitro result in a time-dependent loss of constitutive NOS activity with a partial restoration of enzyme activity during 15 and 45 min ischemia followed by 30 min of reoxygenation. A significant decrease of enzyme activity was found during 60 min ischemia alone, which persisted up to 1 h of oxygen-glucose restoration. The upregulation of neuronal nitric oxide synthase was observed in the ventral horn motoneurons after all ischemic periods. The remarkable changes in optical density of neuronal nitric oxide synthase immunoreactive motoneurons were observed after 45 and 60 min ischemia in vitro followed by 30 and 60 min reoxygenation. 4. Our results suggest that the oxygen-glucose deprivation followed by reoxygenation in the spinal cord is adequately sensitive to monitor ischemia/reperfusion changes. It seems that 15 min ischemia in vivo and 45 min ischemia in vitro cause reversible changes, while the decline of Ca(2+)-dependent nitric oxide synthase activity after 60 min ischemic insult suggests irreversible alterations.

Adult motor neuron apoptosis is mediated by nitric oxide and Fas death receptor linked by DNA damage and p53 activation

The mechanisms of injury- and disease-related degeneration of motor neurons (MNs) need clarification. Unilateral avulsion of the sciatic nerve in the mouse induces apoptosis of spinal MNs that is p53 and Bax dependent. We tested the hypothesis that MN apoptosis is Fas death receptor dependent and triggered by nitric oxide (NO)- and superoxide-mediated damage to DNA. MNs in mice lacking functional Fas receptor and Fas ligand were protected from apoptosis. Fas protein levels and cleaved caspase-8 increased in MNs after injury. Fas upregulation was p53 dependent. MNs in mice deficient in neuronal NO synthase (nNOS) and inducible NOS (iNOS) resisted apoptosis. After injury, MNs increased nNOS protein but decreased iNOS protein; however, iNOS contributed more than nNOS to basal and injury-induced levels of NADPH diaphorase activity in MNs. NO and peroxynitrite (ONOO-) fluorescence increased in injured MNs, as did nitrotyrosine staining of MNs. DNA damage, assessed as 8-hydroxy-2-deoxyguanosine and single-stranded DNA, accumulated within injured MNs and was attenuated by nNOS and iNOS deficiency. nNOS deficiency increased DNA repair protein oxoguanine DNA-glycosylase, whereas iNOS deficiency blocked diaphorase activity. MN apoptosis was blocked by the antioxidant Trolox and by overexpression of wild-type human superoxide dismutase-1 (SOD1). In contrast, injured MNs in mice harboring mutant human SOD1 had upregulated Fas and iNOS, escalated DNA damage, and accelerated and increased MN degeneration and underwent necrosis instead of apoptosis. Thus, adult spinal MN apoptosis is mediated by upstream NO and ONOO- genotoxicity and downstream p53 and Fas activation and is shifted to necrosis by mutant SOD1.

Neonatal loss of motor function in human spina bifida aperta

OBJECTIVE

In neonates with spina bifida aperta (SBA), leg movements innervated by spinal segments located caudal to the meningomyelocele are transiently present. This study in neonates with SBA aimed to determine whether the presence of leg movements indicates functional integrity of neuronal innervation and whether these leg movements disappear as a result of dysfunction of upper motor neurons (axons originating cranial to the meningomyelocele) and/or of lower motor neurons (located caudal to the meningomyelocele).

METHODS

Leg movements were investigated in neonates with SBA at postnatal day 1 (n = 18) and day 7 (n = 10). Upper and lower motor neuron dysfunction was assessed by neurologic examination (n = 18; disinhibition or inhibition of reflexes, respectively) and by electromyography (n = 12; absence or presence of denervation potentials, respectively).

RESULTS

Movements, related to spinal segments caudal to the meningomyelocele, were present in all neonates at postnatal day 1. At day 1, leg movements were associated with signs of both upper (10 of 18) and lower (17 of 18) motor neuron dysfunction caudal to the meningomyelocele. In 7 of 10 neonates restudied after the first postnatal week, leg movements had disappeared. The absence of leg movements coincided with loss of relevant reflexes, which had been present at day 1, indicating progression of lower motor neuron dysfunction.

CONCLUSIONS

We conclude that the presence of neonatal leg movements does not indicate integrity of functional lower motor neuron innervation by spinal segments caudal to the meningomyelocele. Present observations could explain why fetal surgery at the level of the meningomyelocele does not prevent loss of leg movements.

Alteration in intracellular calcium homeostasis reduces motor neuronal viability expressing mutated Cu/Zn superoxide dismutase through a nitric oxide/guanylyl cyclase cGMP cascade

Missense mutations in the human Cu/Zn superoxide dismutase gene (SOD-1) cause many cases of autosomal dominant familial amyotrophic lateral sclerosis (FALS). The accumulation of intracellular calcium is one of the primary mechanisms of motor neuronal degeneration associated with mutations in SOD-1. In order to investigate the effect of various calcium modulators and the SOD-1 mutation on neuronal death, we tested motoneuron-neuroblastoma hybrid (VSC 4.1) cells constitutively expressing human SOD-1 gene with mutations (A4V, G93A) or wild-type. These cells were treated with endogenous calcium releaser (ryanodine, thapsigargin, cyclic ADP-ribose) or calcium mobilizer through cell membrane (4-bromo-calcium ionophore A23187). In particular, calcium ionophore reduced survival in the cells expressing mutant SOD-1. Cell death was associated with increased nitric oxide (NO) generation. This toxicity was attenuated when a nitric oxide synthase (NOS) inhibitor was added. Exogenous NOadministration (S-nitrosoglutathione) also induced cell death. The NO-dependent guanylyl cyclase-cGMP cascade inhibitor protected the mutant cells from the toxic effects of calcium ionophore. Our data suggests that motoneuron degeneration with the SOD-1 mutation may be mediated by calcium dysregulation, particularly by the exogenous calcium influx. This process induces oxidative stress generation that results in motor neuronal death through the guanylyl cyclase-cGMP dependent cascade.

Pentoxifylline reduces biochemical markers of ischemia-reperfusion induced spinal cord injury in rabbits

STUDY DESIGN

Occlusion of the infrarenal abdominal aorta with administration of pentoxifylline was applied to adult rabbits, followed by removal of aortic clamp and reperfusion. Tissue levels of cytokines, lipid peroxides, and antioxidant enzymes were assayed and compared within groups.

OBJECTIVES

To examine the effect of pentoxifylline (PTX) on cytokine levels, lipid peroxidation, and antioxidant enzymes in a rabbit model of spinal cord ischemia-reperfusion injury induced by aortic occlusion.

SETTING

Isparta, Turkey.

METHODS

Rabbits were randomly allocated into four groups of sham laparotomy (SHAM), sham laparotomy with PTX administration (SHAM+PTX), aortic occlusion and reperfusion (AOR), aortic occlusion and reperfusion with PTX administration (AOR+PTX). An intravenous bolus of 50 mg/kg PTX was given just before aortic cross clamping. An atraumatic microvascular clamp was then placed on the abdominal aorta immediately distal to the left renal artery for 30 min. PTX was infused at a rate of 0.5 mg/kg/min during the aortic occlusion. Animals were subjected to 120 min of reperfusion after removal of the aortic clamp. All animals were sacrificed at the end of reperfusion. The lumbosacral segments of spinal cords were quickly harvested and stored at -78 degrees C for biochemical assays of IL-6, TNF-alpha, MDA, SOD, and CAT levels. Differences among groups were analyzed by one-way analysis of variance followed by a post hoc Tukey's honestly significant difference test.

RESULTS

No differences in mean levels of IL-6, TNF-alpha, MDA, SOD, and CAT were noted between SHAM and SHAM+PTX groups (P>0.05). There was a significant increase in all biochemical parameters in the AOR group (P<0.05). Administration of PTX significantly attenuated the levels of all biochemical parameters in the AOR+PTX group (P<0.05).

CONCLUSION

PTX pretreatment attenuated ischemia-reperfusion induced spinal cord injury in a rabbit model, in terms of biochemical parameters of ischemia and reperfusion.

Expression and function of inducible nitric oxide synthase in neurons

Enzymatically derived nitric oxide (NO) has been implicated in numerous physiological and pathological processes in the brain. Whereas during development NO participates in developmental and maturation processes, excess NO production in the adult in response to inflammation, injury, or trauma participates in both cell death and repair. The expression and activity of the inducible isoform of NO synthase (iNOS) play a pivotal role in sustained and elevated NO release. Recent evidence suggests that neurons can respond to proinflammatory stimuli and take part in brain inflammation. Neuronal iNOS expression has been described in different experimental settings, including cytokine stimulation of neuronal cell lines and primary neurons in vitro as well as in animal models of stroke and neurodegeneration. This article outlines different conditions leading to iNOS gene transcription and expression in neurons and neuronal cells and highlights the potential impact on human brain inflammation and neurodegeneration.